1. Field of the Invention
The present invention relates to a solid electrolyte composition, a binder for an all-solid-state secondary battery, and an electrode sheet for batteries, and an all-solid-state secondary battery each using the solid electrolyte composition.
2. Description of the Related Art
An electrolyte solution is used in a lithium-ion battery. There has been an attempt of an all-solid-state secondary battery in which all configuration materials are solid by substituting the electrolyte solution with a solid electrolyte. Above all, the greatest advantage of the technique of using an inorganic solid electrolyte is high safety. As a medium of the electrolyte solution, a combustible material such as a carbonate-based solvent is used for the electrolyte solution used in the lithium-ion secondary battery. Therefore, various safety measures are employed, but there is a concern that inconvenience may occur when a battery is overcharged, and an additional measurement is desired. An all-solid-state secondary battery formed of an inorganic compound that can cause an electrolyte to be incombustible is regarded as a solution thereof.
A second advantage of the all-solid-state secondary battery is that a high energy density is suitably achieved by stacking electrodes. Specifically, the all-solid-state secondary battery can be a battery having a structure in which electrodes and electrolytes are directly arranged side by side to be serialized. At this point, a metal package that seals battery cells and a copper wire or a bus bar that connects battery cells can be omitted, and thus an energy density of the battery can be greatly increased. In addition, it is advantageous that good compatibility with a positive electrode material in which a potential can be enhanced to a high level.
According to the respective advantages as described above, the development of the all-solid-state secondary battery as a next-generation lithium-ion secondary battery is energetically advanced (see NEDO: New Energy and Industrial Technology Development Organization, Fuel Cells-Hydrogen Technology Development Field, Electricity Storage Technology Development Section “NEDO Technology Development Roadmap of Battery for New Generation Vehicles 2008” (June 2009)). Meanwhile, the inorganic all-solid-state secondary battery has a disadvantage caused by the fact that the electrolyte thereof is a hard solid. For example, interface resistance between solid particles increases. In order to overcome this disadvantage, a method of sintering a solid electrolyte in a high temperature (JP2008-059843A), a method of using a jig for pressurizing a cell (JP2008-103284A), a method of covering the entire element with a resin and pressurizing the entire element (JP2000-106154A), a method of pressurizing and baking a green sheet including a solid electrolyte (JP2012-186181A), and the like are suggested.